Increasing the output length of a hash function primarily affects what aspect of security?

• A. Shorter hash length
• B. Larger output length
• C. Reversibility
• D. Deterministic mapping

Answer: (B)

Longer hash outputs expand the hash value space, making brute-force attempts to find a preimage or a collision require more work. Preimage resistance scales with the output length (roughly 2^n attempts for an n-bit output), and collision resistance improves by the birthday bound (roughly 2^(n/2) work). Deterministic mapping and one-way behavior aren’t fundamentally changed by output length, so the main security boost from increasing output length is stronger resistance due to the larger output space.